A detector for detecting information carried by a wobble signal having a sawtooth-like shape with a base frequency of fwob. The detector includes a first band-pass filter having a center frequency close to 2*fwob for filtering the wobble signal and generating a first filtered signal, a second band-pass filter having the center frequency close to fwob for filtering the wobble signal and generating a second filtered signal, first and second comparators for respectively comparing the first and second filtered signal with a reference voltage and generating first and second compared signals, a delay unit for delaying the second compared signal by a time period, and then outputting a delayed signal, and a sampling unit for sampling the first compared signal using the delayed signal as a sampling clock, and for outputting a sampled value representing the information carried by the sawtooth wobble.
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19. A method for detecting information carried by a wobble signal having a sawtooth-like shape, the wobble signal having a base frequency of fwob, the method comprising:
generating a first filtered signal by band-pass filtering the wobble signal using a center frequency close to 2*fwob;
generating a second filtered signal by band-pass filtering the wobble signal using a center frequency close to fwob;
generating a first compared signal by comparing the first filtered signal with a first reference voltage;
generating a second compared signal by comparing the second filtered signal with a second reference voltage;
generating a delayed signal by delaying the first compared signal by a preset time period; and
generating a sampled value representing the information carried by the wobble signal by sampling the delayed signal using the second compared signal as a sampling clock.
13. A method for detecting information carried by a wobble signal having a sawtooth-like shape, the wobble signal having a base frequency of fwob, the method comprising:
generating a first filtered signal by band-pass filtering the wobble signal using a center frequency close to 2*fwob;
generating a second filtered signal by band-pass filtering the wobble signal using a center frequency close to fwob;
generating a first compared signal by comparing the first filtered signal with a first reference voltage;
generating a second compared signal by comparing the second filtered signal with a second reference voltage;
generating a delayed signal by delaying the second compared signal by a preset time period; and
generating a sampled value representing the information carried by the wobble signal by sampling the first compared signal using the delayed signal as a sampling clock.
7. A detector for detecting information carried by a wobble signal having a sawtooth-like shape, the wobble signal having a base frequency of fwob, the detector comprising:
a first band-pass filter, which has a center frequency close to 2*fwob, for receiving and filtering the wobble signal and generating a first filtered signal;
a second band-pass filter, which has a center frequency close to fwob, for receiving and filtering the wobble signal and generating a second filtered signal;
a first comparator for comparing the first filtered signal with a first reference voltage and generating a first compared signal;
a second comparator for comparing the second filtered signal with a second reference voltage and generating a second compared signal;
a delay unit for receiving the first compared signal, delaying the first compared signal by a preset time period, and then outputting a delayed signal; and
a sampling unit for sampling the delayed signal using the second compared signal as a sampling clock, and outputting a sampled value representing the information carried by the wobble signal.
1. A detector for detecting information carried by a wobble signal having a sawtooth-like shape, the wobble signal having a base frequency of fwob, the detector comprising:
a first band-pass filter, which has a center frequency close to 2*fwob, for receiving and filtering the wobble signal and generating a first filtered signal;
a second band-pass filter, which has a center frequency close to fwob, for receiving and filtering the wobble signal and generating a second filtered signal;
a first comparator for comparing the first filtered signal with a first reference voltage and generating a first compared signal;
a second comparator for comparing the second filtered signal with a second reference voltage and generating a second compared signal;
a delay unit for receiving the second compared signal, delaying the second compared signal by a preset time period, and then outputting a delayed signal; and
a sampling unit for sampling the first compared signal using the delayed signal as a sampling clock, and outputting a sampled value representing the information carried by the wobble signal.
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This application claims the benefit of the filing date of Taiwan Application Ser. No. 092128013, filed Oct. 8, 2003, the content of which is incorporated herein by reference.
The invention relates to a detector for detecting information carried by signal having a sawtooth-like shape.
Along with advances in optical disc technologies, a new generation of the optical disc rewritable format that is defined as the Blu-Ray has been developed. The track groove in the Blu-Ray optical disc has a wobble shape, and the basic wobble pattern of the track groove is a sine/cosine wave. In the Blu-Ray optical disc, one nominal wobble length (referred to as NWL hereinafter) is equivalent to 69 channel bits, which is the minimum record unit of the Blu-Ray optical disc.
The basic pattern of the wobble is a cosine wave: cos{2π*fwob*t}, where fwob denotes the basic frequency of the wobble. Wobbles in this basic shape are called “Monotone Wobbles” (MW). In addition, some wobbles are modulated in order to carry the address information which are referred to as the ADIP (Addresses in Pre-groove), of some record units on the disc, wherein two modulation methods are involved. The first modulation method is the minimum shift keying—cosine variant (referred to as MSK-cos hereinafter), and the second method is the harmonic modulated wave (referred to as HMW hereinafter).
a first NWL starts MSK mark with a cosine wobble with a frequency 1.5* fwob, and is given by cos{2π*(1.5*fwob)*t};
a second NWL continues the MSK mark with a cosine wobble with a frequency fwob, and is given by −cos {2π*fwob*t}; and
a third NWL terminates the MSK mark with a cosine wobble with a frequency 1.5*fwob, and is given by −cos{2π*(1.5*fwob)*t}.
cos{2π*fwob*t}±a*sin {2π*(2*fwob)*t} in which a=0.25.
Such a combination of a cosine signal with the basic frequency fwob and a weighted second harmonic signal forms a sawtooth-like waveform. The “+” or “−” sign creates the left or right inclination of the waveform, where the “+” sign is used to represent an information bit of logic one, while the “−” sign is used to represent an information bit of logic zero.
monotone unit: consisting of 1 MM followed by 53 MW;
reference unit: consisting of 1 MM followed by 15 MW, 37 STW, and 1 MW;
sync—0 unit: consisting of 1 MM followed by 13 MW, 1 MSK mark, 7 MW, 1 MM, and 27 MW;
sync—1 unit: consisting of 1 MM followed by 15 MW, 1 MSK mark, 7 MW, 1 MM, and 25 MW;
sync—2 unit: consisting of 1 MM followed by 17 MW, 1 MM, 7 MW, 1 MM, and 23 MW;
sync—3 unit: consisting of 1 MM followed by 19 MW, 1 MM, 7 MW, 1 MM, and 21 MW;
data—1 unit: consisting of 1 MM followed by 9 MW, 1 MM, 3 MW, 37 STW, and 1 MW; and
data—0 unit: consisting of 1 MM followed by 11 MW, 1 MM, 1 MW, 37 STW, and 1 MW.
Hence, the ADIP addresses on the optical disc are positioned according to the unit types of the above-mentioned ADIP unit. So, in order to judge the unit types of the ADIP unit correctly, it is an important subject to correctly judge whether the information bit carried by the STW is logic one or logic zero.
In view of the above-mentioned problems, an object of the invention is to provide a detector for detecting information carried by a wobble signal having a sawtooth-like shape.
To achieve the above-mentioned object, the detector of the invention includes a first band-pass filter having a center frequency close to 2*fwob for filtering the wobble signal and generating a first filtered signal, a second band-pass filter having a center frequency close to fwob for filtering the wobble signal and generating a second filtered signal, a first comparator for comparing the first filtered signal with a reference voltage and generating a first compared signal, a second comparator for comparing the second filtered signal with the reference voltage and generating a second compared signal, a delay unit for receiving the second compared signal, delaying the second compared signal by a time period, and then outputting a delayed signal, and a sampling unit for sampling the first compared signal using the delayed signal as a sampling clock, and outputting a sampled value representing the information bit carried by the wobble signal.
To achieve the above-mentioned object, the detector of the invention includes a first band-pass filter having a center frequency close to 2*fwob for filtering the wobble signal and generating a first filtered signal, a second band-pass filter having a center frequency close to fwob for filtering the wobble signal and generating a second filtered signal, a first comparator for comparing the first filtered signal with a reference voltage and generating a first compared signal, a second comparator for comparing the second filtered signal with the reference voltage and generating a second compared signal, a delay unit for receiving the first compared signal, delaying the first compared signal by a time period, and then outputting a delayed signal, and a sampling unit for sampling the delayed signal using the second compared signal as a sampling clock, and outputting a sampled value representing the information bit carried by the wobble signal.
The detector for detecting information carried by signal having a sawtooth-like shape of the invention will be described with reference to the accompanying drawings.
The first band-pass filter 51 has a center frequency, substantially twice that of the base frequency fwob of the wobble signal in this embodiment, and generates a first filtered signal BF1. The second band-pass filter 52 has a center frequency, substantially equal to the base frequency fwob of the wobble signal in this embodiment, and generates a second filtered signal BF2. Hence, after the wobble signal passes through the first band-pass filter 51, the base frequency component is substantially filtered out and the double-frequency component is kept. Thus, the first filtered signal BF1 can be given by,
BF1=±a*sin {2π*(2*fwob)*t}
wherein the “+” or “−” sign represents the polarity of the first filtered signal BF1.
On the other hand, after the wobble signal passes through the second band-pass filter 52, the double-frequency component is substantially filtered out and the base frequency component is kept. Thus, the second filtered signal BF2 can be given by,
BF2=cos{2π*fwob*t}
The first comparator 53 converts the first filtered signal BF1 into a square wave first compared signal CS1, and the second comparator 54 converts the second filtered signal BF2 into a square wave second compared signal CS2. For practical implementation, the first comparator 53 and the second comparator 54 could be a traditional comparator, a slicer, or the like such that when the level of the input signal is higher than a reference signal Vref, logic high, typically having a high voltage level, is outputted; or otherwise logic low, typically having a low voltage level, is outputted. The delay unit 55 receives the second compared signal CS2 and delays the second compared signal CS2 by a time period Td to generate a delayed signal DS1. Theoretically, the time period Td can be any positive number. For practical system, it is preferred that the time period Td is less than 1/fwob, and even preferred that Td equals to N/(8*fwob), where N is an odd integer. The sampling unit 56 samples the first compared signal CS1 using the delayed signal DS1 as a trigger signal, and outputs the sampled value Q which reflects the information bit carried by the sawtooth wobble signal. The sampling unit 56 may be a flip-flop, or other circuits that can provide the equivalent function.
It can be found that it is the first compared signal CS1 which reflects the information carried by the sawtooth wobble signal. To speak more specifically, the polarity of the first compared signal CS1 reflects the information carried by the sawtooth wobble signal. The polarity of the first compared signal CS1 can be detected based on the sampled value Q obtained by sampling the first compared signal CS1. The second compared signal SC2 is a good candidate of the sampling clock used for sampling the first compared signal SC1. However, as will be seen in
Followings are the steps of a first method for detecting information carried by a wobble signal having a sawtooth-like shape in the present invention. The wobble signal has a base frequency of fwob. The method comprises:
Step S1202: generate a first filtered signal by band-pass filtering the wobble signal using a center frequency close to 2*fwob.
Step S1204: generate a second filtered signal by band-pass filtering the wobble signal using a center frequency close to fwob.
Step S1206: generate a first compared signal by comparing the first filtered signal with a first reference voltage.
Step S1208: generate a second compared signal by comparing the second filtered signal with a second reference voltage. The first reference voltage and the second reference voltage may be substantially the same.
Step S1210: generate a delayed signal by delaying the second compared signal by a preset time period. The preset time period is less than 1/fwob and equals to N/(8*fwob), wherein N is an odd integer.
Step S1212: generate a sampled value representing the information carried by the wobble signal by sampling the first compared signal using the delayed signal as a sampling clock. The delayed signal can be sampled according to the rising edges or falling edges of the second compared signal to generate the sampled value.
The delay unit 95 receives the first compared signal CS1 and delays the first compared signal CS1 by a time period Td to generate a delayed signal DS1. Theoretically, the time period Td can be any positive number. For practical system, it is preferred that the time period Td is less than 1/fwob, and even preferred that Td equals to N/(8*fwob), where N is an odd integer. The sampling unit 56 samples the delayed signal DS1 using the second compared signal CS2 as a trigger signal, and outputs the sampled value Q which reflects the information carried by the sawtooth wobble signal. The sampling unit 56 may be a flip-flop, or other circuits that can provide the equivalent function.
It can be found that it is the first compared signal CS1 which reflects the information carried by the sawtooth wobble signal. To speak more specifically, the polarity of the first compared signal CS1 reflects the information carried by the sawtooth wobble signal. The polarity of the first compared signal CS1 can be detected based on the sampled value Q obtained by sampling the delayed signal DS1 obtained by delaying the first compared signal CS1 by a time period Td. The second compared signal SC2 is a good candidate of the sampling clock used for sampling the delayed signal DS1.
Followings are the steps of a second method for detecting information carried by a wobble signal having a sawtooth-like shape in the present invention. The wobble signal has a base frequency of fwob. The method comprises:
Step S1302: generate a first filtered signal by band-pass filtering the wobble signal using a center frequency close to 2*fwob.
Step S1304: generate a second filtered signal by band-pass filtering the wobble signal using a center frequency close to fwob.
Step S1306: generate a first compared signal by comparing the first filtered signal with a first reference voltage.
Step S1308: generate a second compared signal by comparing the second filtered signal with a second reference voltage. The first reference voltage and the second reference voltage may be substantially the same.
Step S1310: generate a delayed signal by delaying the first compared signal by a preset time period. The preset time period is less than 1/fwob and equals to N/(8*fwob), wherein N is an odd integer.
Step S1312: generate a sampled value representing the information carried by the wobble signal by sampling the delayed signal using the second compared signal as a sampling clock. The delayed signal can be sampled according to the rising or falling edges of the second compared signal to generate the sampled value.
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific construction and arrangement shown and described, since various other modifications may occur to those ordinarily skilled in the art. detector for detecting information carried by a signal having a sawtooth-like shape, the detector comprising:
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